This invention relates to a reclaiming and stacking system for handling bulk material, such as coal; it finds particular use in coal-fired power plants for moving the coal to its final point of utilization.
According to a known coal transporting system, the coal, stacked at a remote location in the plant area, is moved to a rail-mounted stacker/reclaimer apparatus by means of an upwardly sloping conveyor belt assembly forming part of a separate travelling tripper. From the latter, the coal is transferred to the boom belt of the stacker/reclaimer apparatus which stacks out the coal to form a coal pile on one side of a yard conveyor extending parallel with the rails under the stacker/reclaimer apparatus. The outer end of the boom is provided with a bucket wheel, by means of which coal can be reclaimed from the coal pile and conveyed by the reversible boom conveyor belt to the yard conveyor. The boom of the stacker/reclaimer is slewable (that is, rotatable about a vertical axis), so that coal supplied by the travelling tripper can also be stacked out on another pile on the other side of the yard conveyor. Thus, the stacker/reclaimer apparatus may retrieve material from either the one or the other pile by means of the slewable stacker and reclaimer boom and transfer the bulk material from the inner end of the boom conveyor to the yard conveyor. This system is, however, not adapted to directly transfer coal -- in a single operation -- from one coal pile to form a second coal pile on the other side of the yard conveyor.
In another known reclaiming and stacking system -- as disclosed, for example, in German published patent application (Auslegeschrift) No. 1,299,913 -- there is provided a rail-mounted apparatus and a ground-supported, reversible, yardbelt disposed between the rails and adapted to move coal either from a certain remote location to the apparatus or, when the belt travel direction is reversed, to convey coal from the apparatus to the same remote location. For this purpose, the upper reach of the reversible yard conveyor rises in the zone of the rail-mounted apparatus, forms a trigger loop, and then redescends to continue its course along the rails. The reversible yard conveyor has a lower reach which, throughout its course, extends at ground level beneath the upper reach. At all times -- that is, regardless of the direction in which the reversible conveyor is driven -- only that portion of the upper reach of the yard conveyor moves coal that is situated between the rail-mounted apparatus and one end of the reversible yard conveyor. The rail-mounted apparatus has a reclaimer boom and a stacker boom supported on a slew platform. The apparatus can perform essentially three types of operations: first, the coal or other bulk material transported on the reversible yard conveyor to the apparatus is, by gravity, transferred to the stacker belt and thus piles may be formed on the one and the other side of the apparatus rails by means of the slewable stacker boom. Second, coal from the piles can be reclaimed by a bucket wheel mounted at the outer end of the reclaimer boom. The material is transferred from the reclaimer conveyor to the reverisible yard conveyor on which then the material is transported towards the same location from which it had been earlier supplied to the apparatus for stacking. Third, material can be transferred from one pile on one side of the rails to the other pile on the other side of the rails by transferring material from the reclaimer conveyor onto the reversible yard conveyor and therefrom onto the stacker conveyor from the outer end of which the material is ejected to form a second pile. It is noted that this third operation must be considered as particularly uneconomical and energy-wasting because of the necessity of operating the reversible yard conveyor -- which may have a length of thousands of feet -- for a few feet of utilized length within the rail-mounted apparatus.
It is seen that in the precedingly described known system a yard conveyor with a travelling tripper is needed for transferring the material in all three types of the conveying operation.
According to another conventional coal moving method, coal is shipped from the coal mine in unit trains which have bottom-discharge box cars and which arrive on trestles in the power plant area. The coal is discharged from the box cars and thus a coal pile is formed beneath the trestles which extend along one side of a yard conveyor belt leading to the plant furnaces. A single-purpose reclaimer apparatus which runs on rails along the yard conveyor retrieves material from the coal pile at the trestles and deposits it onto the yard conveyor belt by gravity. If it is desired, for the purpose of increasing the live storage capacity, to build a second pile on the other side of the yard conveyor from the coal in the first pile under the trestles, a second, stacking apparatus has to be called in for cooperation with the single-purpose reclaimer to thus effect a transfer of the coal from the first pile to the second pile. The coal may then be reclaimed by the slewable single-purpose reclaimer from either the one or the other pile.
There is further known an excavator and stacking apparatus which comprises a crawler-mounted, slewable platform which supports an excavator boom provided at its outer end with a bucket wheel, as well as a stacker boom. Between the discharge end of the excavator belt and the charging end of the stacker belt there is provided a transfer belt for transferring material within the apparatus, from the excavator belt to the stacker belt. This known apparatus is concerned exclusively with the stacking of excavated material in a single operation by transferring the excavated material from the excavator belt to a transfer belt and from the transfer belt to the stacker belt. There is no provision of a yard conveyor cooperating with and disposed beneath the apparatus; such an arrangement would further not be feasible since the excavator/stacker apparatus does not move in a fixed path.